Want to Look Skinnier New Year's Eve?

You want to look hot on New Year's Eve—it's a given. Ask any fashion stylist for their best tip on dressing for your shape, and she'll tell you it's what you put on* under *your clothes that matters the most. Annabel Tollman, who has worked with Scarlett Johansson, Mandy Moore, and America Ferrera, gave Allure all her tips on finding the best shapewear.

Look for slippery finish. Shapewear not only holds in the parts that you want minimized—your tummy, your butt, or even your back—but it helps clothes fit and hang better. "Pick a slippery, shiny finish, rather than a matte one," says Tollman. "Your clothes will glide over it." She recommends the Donna Karen Body Perfect line.

Round up. A lot of women think that the tighter they go, the skinnier they'll look. Not true. "It can be tempting to get a tight undergarment, but if you squeeze your flesh in one area, it's going to pop out in another," say Tollman. You should be able to breathe—and even, gasp, eat—when you sit down. If you're between sizes, always go up rather than down. If the shapewear bunches, rides up, or rolls at the top, that's because it's too small.

Know your target. You don't have to encase yourself neck to knees. Choose shapewear that's designed specifically for the body part that concerns you the most. If that's your belly, look for seamless underpants or a high-waisted thong—Tollman recommends the ones by Yummie Tummie—or a style that goes all the way to the bra line, such as Spanx Higher Power. Camisoles with built-in bras will take care of back bulge or muffin top; these are also great if you're worried about a visible waistband. If the problem is your butt or thighs, get the shorts, but make sure you don't have a big ridge of elastic at the thigh.

Know when to skip it. There is nothing worse than seeing flesh-colored shorts through the slit at the back of a woman's skirt. "It's far better to skip shapewear altogether than for anyone to see it," says Tollman.